Experimental evidence for homoclinic chaos in an electrochemical growth process

Argoul, Françoise; Huth, John M.; Merzeau, Pascal; Arnéodo, A.; Swinney, Harry L.

doi:10.1016/0167-2789(93)90279-a

Cited by 45 publications

(11 citation statements)

References 66 publications

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“…Van Hassel et al 9 The present study is aimed at an assessment of electrochemical properties of doped lanthanum chromites under conditions of SOFC operation. On the basis of our previously reported data of electrical conductivity and the oxygen vacancy diffusion coefficient as well as the pointdefect model to elucidate a defect equilibrium,5"215 a model is proposed to calculate the distribution of oxygenchemical potential (simply termed as oxygen potential profile throughout this paper), ionic leak current density, and specific area resistance of LaCrO3-based interconnectors.…”

Section: Resultsmentioning

confidence: 99%

A Model for Nanolaminated Growth Patterns in Zn and Zn‐Co Electrodeposits

Yan

Downes

Boden

et al. 1996

J. Electrochem. Soc.

100

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A hydroxide oscillation model has been proposed to account for the observed "nanolaminated" structure in electrodeposited Zn and Zn-Co alloys produced under potentiostatic control. At a critical cathode potential the Zn deposition proceeds in a cyclically changing environment arising from the regular formation and decay of a zinc hydroxide layer near the cathode surface, which produces Zn-ZnO laminations in the deposits. Co was found to enrich at the Zn-ZnO interface. Such a model is supported by evidence obtained from electrochemical measurements and transmission electron microscopy observations, and this has given some insight into the anomalous behavior of Zn-Co deposition. lnfroduction In the electrodeposition of Zn-Co alloys from an acid sulfate solution, anomalous deposition' occurs in which the less noble metal Zn is deposited preferentially. A model proposed by Dahms et al.2 suggested that the deposition proceeded with the intermediate formation of a metal hydroxide located in the vicinity of the electrode and this inhibited the deposition of more noble metal.Higashi et al.4 have measured the pH in close approximation to the cathode while anomalous codeposition of ZnCo was taking place. It was shown that an abrupt rise in pH to values in the range 5.0 to 5.5 occurred, which would permit zinc hydroxide precipitation. These findings promoted the development of the "hydroxide suppression mechanism"24 for the anomalous deposition of Zn-iron group metal alloys which include Zn-Co.Observations by the authors6'7 using transmission electron microscopy (TEM) have shown that Zn and Zn-Co alloy deposits produced under galvanostatic conditions on a steel substrate contain a series of nanolaminations.These exist in a regular pattern with 50 nm thick Zn crystals surrounded by a ZnO layer which is 3 to 4 am thick. In the alloy the Co was found to be preferentially accommodated at the Zn-ZnO boundary. Here, the authors have carried out a polarization study on the Zn and Zn-Co plating solutions with polycrystalline steel and zinc singlecrystal cathode substrates. Zn and Zn-Co deposits have then been produced under potentiostatic control and examined by TEM and scanning electron microscope (SEM). Particular attention has been given to the onset of anomalous deposition. The information gained has been used to set up a new model to account for anomalous deposition of zinc and its alloys. ExperimentalPlating solutions.-Zn and Zn-Co coatings were electrodeposited from an acidic sulfate solution on to either a mild steel substrate or on to a (0001) faced single-crystal zinc substrate. The substrates were disk shaped, 1 cm2 surface area, which had been polished with 1 m diamond compound. Prior to plating they were given an ultrasonic clean. Table I lists the compositions of the solutions employed.Cathodic polarization study.-Polarization studies were carried out in a standard three-electrode cell. The cathode was immersed in 1 liter of aerated solution and Luggin capillary [in contact with an external saturated calomel electrode...

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Section: Resultsmentioning

confidence: 99%

A Model for Nanolaminated Growth Patterns in Zn and Zn‐Co Electrodeposits

Yan

Downes

Boden

et al. 1996

J. Electrochem. Soc.

100

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“…Both numerical as well as analytical studies have been carried out extensively to the explain the origin of the MMOs and the complex bifurcation sequences these systems exhibit [9][10][11][12][16][17][18][19][20][21][22][23]. Even though the origin of complex bifurcation sequences and the accompanying MMOs may depend on the particular system under study, almost all proposed mechanisms suggest that these bifurcation portraits are the artefact of global bifurcations of the system [17].…”

Section: Introductionmentioning

confidence: 99%

“…These periodic states are characterized by combinations of relatively large amplitude excursions and small amplitude near harmonic oscillations of the trajectories and have been referred to as mixed mode oscillations (MMOs) in the literature. The MMOs and the accompanying complex bifurcation sequences have been observed in models and experiments in various fields of chemical kinetics [1][2][3][4][5][6][7][8], electrochemical reactions [9][10][11][12], biological systems [13], and in many other physical systems [14,15].…”

Section: Introductionmentioning

confidence: 99%

Incomplete approach to homoclinicity in a model with bent-slow manifold geometry

Rajesh

Ananthakrishna

2000

Physica D: Nonlinear Phenomena

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Abstract:The dynamics of a model, originally proposed for a type of instability in plastic flow, has been investigated in detail. The bifurcation portrait of the system in two physically relevant parameters exhibits a rich variety of dynamical behaviour, including period bubbling and period adding or Farey sequences. The complex bifurcation sequences, characterized by Mixed Mode Oscillations, exhibit partial features of Shilnikov and Gavrilov-Shilnikov scenario. Utilizing the fact that the model has disparate time scales of dynamics, we explain the origin of the relaxation oscillations using the geometrical structure of the bent-slow manifold. Based on a local analysis, we calculate the maximum number of small amplitude oscillations, s, in the periodic orbit of L s type, for a given value of the control parameter. This further leads to a scaling relation for the small amplitude oscillations. The incomplete approach to homoclinicity is shown to be a result of the finite rate of 'softening' of the eigen values of the saddle focus fixed point. The latter is a consequence of the physically relevant constraint of the system which translates into the occurrence of back-to-back Hopf bifurcation. PACS number(s): 05.45. Ac,

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“…Electrochemical reactions with non-linear kinetics give rise to various dynamic self organization phenomena such as oscillations and spatio-temporal pattern formation [9][10][11][12]. Amongst various self-organization phenomena, oscillatory electrodeposition [5,6,9,[13][14][15][16][17] and electropolymerization phenomena are very interesting from the point of view of production of micro and nanostructured materials. Conducting polymers are at present intensively studied in view of their multiple potential technological applications [1,2,[18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%